Multiple mechanism model for photoluminescence from oxidized porous Si

In order to explain experimental results for photoluminescence (PL) from porous silicon (PS), a novel multiple mechanism model is suggested. There are three types of competitive photoexcitation-photoemission processes in PS; and which of them dominates, is usually determined by the oxidation degree of the PS. For a PS sample free from oxidation, the process that both photoexcitation and photoemission of electron-hole pails occur within nanometer silicon particles (NSPs) is dominating. For most oxidized PS samples, the process with the photoexcitation occuring in NSPs, but photoemission occuring in luminescence centers in the SiOx layers surrounding the NSPs, dominates. When NSPs in oxidized PS samples have very small density or very small or large sizes, the process that both photoexcitation and photoemission occur in Si oxide layers is dominating.